I was operating the IC7000 on my desk when it emitted smoke. I quickly turned off and opened up to investigate. I confirmed that the pre-driver board was blackened, which according to web searches appears to be a common failure mode with this rig.
I ordered a new transistor from a UK supplier at a cost of UKP15. Removing the pre-driver PCB wasn't particularly difficult and after some effort and help from a friend was able to remove the old surface mount transistor from its tiny PCB and replace it with the new one (but I would recommend to anyone else to buy a new complete pre-driver board assembly!). Surprisingly there was no sign of thermal grease having been applied between the transistor and the heatsink/case, so I added this for the new transistor. It all went back together OK.
I followed the instructions for setting (what I believe to be) the pre-driver idle current for each frequency band - there are four settings: HF/50-1; HF50-2; 144M; and 430M. The HF/50 and 430M settings adjusted OK, but worryingly the current on the 144M setting didn't change from the base value.
My question is - does this point to the finals transistor having blown?
The strange thing is that operating the rig in FM mode on 144MHz it does put out 40W of power, which would surprise me if the finals transistor was toast. In USB mode when viewing the power meter the needle doesn't move much except on loud sylables. It sort of makes me think that the bias is missing as if the transistor is operating in class C. Perhaps its just wishful thinking that the final transistor is OK.
Has anyone seen similar behaviour?
regards...
--Gary (M1GRY)
Steve W3AHL